[sdiy] Filter bank design

[jhaible at debitel.net]

> That is why I built my bank with 6x6 subbanks with variable Q on each bank, 
> and, additionally, why I put a fader on each of the 36 channels.  I can 
> reduce the density anywhere by just turning some of the channels down.  I 
> can also turn down the Q at low frequencies and set up some broader low 
> frequency formant-type resonances.  Then I can use the higher subbanks for 
> the high-Q timbral enrichment.
> 
> A cool design if you are mainly interested in string simulation might be to 
> have a few parametric-EQ-type filters for low frequencies combined with a 
> dense fixed-frequency bank above something like 500 Hz or so.


Hi Ian - thanks for confirming this. The FB will be considerably smaller
then.

I will probably do a little variation: A LPF, to cover the low range,
in parallel with the BPFs in the kHz range. Then running the whole thing
in series with a parametric EQ. 

Maybe a FB that's restricted to 500Hz ... 10kHz could even comfortably
done with LC filters (as the biggest inductors would be in the lower
bands), but this would either mean winding my own inductors, or using
standard L values (and selected C's of course) and having slightly 
different Q from one BPF to the next.
But probably I'll use an LC filter topology with gyrators.

JH.




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